Researchers find oil impacts in developing fish

Researchers have found abnormalities and development problems in killifish embryos exposed to oiled sediment. The killifish is a popular and abundant marsh bait fish that scientists say make it a “canary in the coal mine” for spill effects.

Last Modified: Wednesday, May 8, 2013 at 8:08 p.m.

Researchers have found abnormalities and development problems in killifish embryos exposed to oiled sediment. The killifish is a popular and abundant marsh bait fish that scientists say make it a “canary in the coal mine” for spill effects.

Ben Dubansky, LSU

Oil exposure caused serious effects including heart defects, delayed hatching, reduced overall hatching and general listlessness in killifish, according to new research from scientists at Louisiana State University, University of California, Davis and Clemson University.

The group's research has used this environmental indicator species to determine the extent of exposure of field-caught fish as a “canary in the coal mine,” said Fernando Galvez, LSU associate biology professor and one of the principle investigators on the project.

“Although the Deepwater Horizon oil spill has passed the attention of most of the nation, our data warn of developmental abnormalities in coastal fish that should be further investigated,” Galvez said.

This is the second study published on Gulf killifish by the scientists, who have tracked the 2010 spill's impact on the popular bait fish. In a 2011 LSU study, scientists found tissue damage and gene changes consistent with oil exposure that could cause developmental and reproductive problems in fish.

Galvez said scientists chose the killifish because they're abundant and important in the marsh food chain, providing a meal for many popular sport fish. The killifish also spend their lives in a confined area of marshes, unlike other species that divide their time between the Gulf and estuaries.

The fish had alterations in heart development, significantly reduced heart rates and delays in hatching. Some of the killifish wouldn't hatch at all. If scientists helped them, the newly hatched fish barely moved. They also saw increased hemorrhaging in the fish that survived and water around the heart.

“Adult fish collected from heavily oiled locations in Louisiana marshes showed evidence of exposure to crude oil long after the visible oil had disappeared from view, and when Gulf killifish embryos were exposed to sediments collected from the most oiled location, their overall hatching success was significantly reduced. There was a time delay in hatching, and this was associated with developmental heart defects in these fish,” said Benjamin Dubansky, a recent LSU PhD graduate. He was first author on the manuscript. “The developmental deformities found are textbook effects that we see when fish are exposed to the toxicants in crude oil and indicate that the developmental success of these fish in the field may be compromised.”

In oiled areas, it was difficult to catch killifish, and the ones researchers found were smaller than normal, Galvez said. Even in the lab, the fish never grew to expected sizes.

Andrew Whitehead, University of California, Davis assistant professor of environmental toxicology, co-principal investigator and co-author on the paper, said other important species such as redfish, speckled trout, flounder, blue crabs, shrimp and oysters are at risk of similar effects.

“What is currently unknown is the capacity of affected populations to buffer or absorb the impacts of these types of developmental effects,” Whitehead said. “However, our research has linked exposure to oil to the molecular responses that initiate toxic effects and now to negative impacts on the well-being of an important ecological indicator species — our ‘canary in the coal mine.' ”

Galvez said scientists sampled a large ecosystem in Barataria Basin that suffered a variety of oil impacts.

The study raises questions about how these changes in biology caused by low-level exposure will affect the survivability and ability of species to deal with infections, parasites or other challenges.

Despite the impact oil had on the fish's development, Galvez said that doesn't mean that Louisiana's seafood is unsafe to eat. The animals are showing biological responses to oil exposure but aren't accumulating hydrocarbons in their meat, he said.

“We can argue that Louisiana's seafood is safe to eat, but the oil that was deposited is having a significant effect on our environment that we have to monitor and take into account,” Galvez said.

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